[Cluster-devel] Re: [NFS] [PATCH 0/4 Revised] NLM - lock failover

[J. Bruce Fields]

On Thu, Apr 05, 2007 at 05:50:55PM -0400, Wendy Cheng wrote:
> 1) Failover server exports filesystem with "fsid" option as:
>     /etc/exports entry> /mnt/shared/exports *(fsid=1234,sync,rw)
> 2) Failover server dispatch rpc.statd with "-H" option.
> 3) Failover server drops locks based on fsid by:
>     shell> echo 1234 > /proc/fs/nfsd/nlm_unlock
> 4) Takeover server enters per fsid grace period by:
>     shell> echo 1234 > /proc/fs/nfsd/nlm_set_igrace
> 5) Takeover server notifies clients for lock reclaim by:
>     shell> /usr/sbin/sm-notify -f -v floating_ip_address -P an_sm_directory

I don't understand statd and lockd as well as I should.  Where exactly
does the takeover server stop serving requests, and the failover server
start?  If this isn't done carefully, you can leave a window between
steps 3 and 4 where a client could acquire a lock before its rightful
owner reclaims it, right?

--b.